Large diameter clay pipes are used for drainage systems and are generally molded with an enlarged bell end while the opposite or spigot end of the pipe is machined to form a groove. On installation, the spigot end is inserted within the bell end of a second pipe and the joint between the pipes is sealed.
Because of the enlarged bell at the end of the pipe, clay pipes in the past have been molded rather than being extruded. In the molding operation, the pipe is formed vertically and the length of the pipe is limited to about eight feet due to the slump characteristics of the clay when it is removed from the mold.
As the bell end projects laterally from the pipe, it is fragile and is subject to breakage during handling and transporting. Furthermore, during laying of the pipe it is customary to shift the pipes by prying with a crowbar and this occasionally will cause breakage of the bell end. Moreover, it is frequently necessary to dig a trench in the ground to accommodate the enlarged diameter bell when laying the pipes for drainage purposes.
As a further disadvantage, the enlared diameter bell end reduces the number of pipes that can be stacked in the furnace during firing of the clay.
To eliminate the problems associated with the bell on large diameter clay pipe, it has been proposed to apply a fiber reinforced resin bell to a cylindrical clay pipe. The fiber reinforced resin bell has the advantage of being substantially stronger than the clay bell, thereby reducing the likelihood of breakage during storage, handling or installation. The fiber reinforced resin bell can be applied to an extruded cylindrical pipe rather than a molded pipe and this enables substantially longer lengths of the large diameter pipe to be utilized.